McGinnis said surveillance video from the casino showed the same man watching the victims of the five connected robberies as they cashed out at the Waterfront gaming hall.
The spotter then apparently calls two accomplices who follow the patrons in a car and then rob them when they arrive home.
The pattern emerged when the stickupmen used a Taser on the victims of the latest robberies, including a pregnant woman, in the early morning hours of Sunday and Tuesday, McGinnis said.
After determining that the victims had been to the SugarHouse, investigators started reviewing casino surveillance video and checking other robberies in the city to see if the victims also had just returned home from a night of gambling.
"You can imagine the hours of video that had to be viewed," he said.
The three other connected robberies occurred Sept. 13, Aug. 30 and Aug. 15.
Police released video of the suspected spotter as well as of two cars used by team members. The spotter appears to drive a Monte Carlo, while the stickupmen in at least one instance left in a Toyota Camry or Ford Focus, detectives said.
McGinnis said the five robberies connected by video showing the spotter on the lookout in the casino all occurred in different parts of the city and all of the victims were Asian.
Of the five robberies possibly connected to the crime team, four, also involving Asians, took place in the city, while the fifth involved a non-Asian victim and occurred in Lower Moreland Township.
Four of the victims, including the pregnant woman, required treatment at a hospital following the robberies.
McGinnis said investigators are looking at more stickups to see if they are connected.
Anyone with information is asked to call the tip line at (215) 686-4877.
Contact Joseph Gambardello at 215-854-2153 or firstname.lastname@example.org